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Lock cylinder difficult to operate

Lock cylinder difficult to operate

My uPVC Door Lock Mechanism is Sticking (causing a problem)

If your lock mechanism is stiff or sticking, or you are having general locking mechanism problems then don’t ignore it. If you don’t resolve the problem you could get to a point where your uPVC door won’t lock. And, then you have an unsecured property that you need to deal with as a matter of urgency.


There are three main reasons why a door lock mechanism is stiff or sticking:


  1. Debris in the lock
  2. Extremes of temperature
  3. A broken lock mechanism or gearbox

uPVC door locking mechanism problems

The first question to ask yourself: Does the lock turn in the open position?


Yes – then there is an issue with the lock mechanism connecting in the frame – read how to adjust a uPVC door hinges.


No – the lock is most likely broken and will need to be replaced – read how to change a lock on a uPVC door.

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uPVC door lock mechanism stiff and sticking

The next question to ask: is the key stiff to turn in the open position?


Yes – this could be due to a build up of dirt, or extreme temperatures, see below

No – the cylinder fixing screw could be loose, see below.



If the key is stiff in the uPVC door lock with the door open

Locks can become stiff to operate due to issues such as dirt in the lock cylinder and lack of maintenance of the locking system. Hopefully, at this point your lock can still be saved with some attention.



To lubricate a uPVC door mechanism you can use:

  • Light machine oil – Like a sewing machine oil. You want as light a grade of oil as possible to avoid creating gunge up the lock.
  • Graphite powder – You can easily buy this online (it’s basically the substance that pencil lead is made out of). Blow the powder into the lock cylinder and this should make the movement of the key smoother.
  • Pro tip: If you don’t have the graphite powder, you can try a graphite pencil. Use the pencil on the key to cover it in pencil lead and then insert the key into the lock and turn a few times.

Do not use WD 40 or 3 in 1 oil on a uPVC door lock as it can damage the uPVC door or create gunge in the lock.


If this doesn’t work, then we recommend that you contact the manufacturer or a trained locksmith who can help you to replace the lock on a uPVC door.



If the key is stiff only when the uPVC door is closed

  • Adjust the cylinder fixing screw - the screw that holds the lock cylinder to the door. The screw would be visibly proud of the lock plate, or it might be too tight, in this case, slacken the screw with a half turn. The screw should feel snug but not forced to turn.
  • Check if the door is too hot or cold - In extreme temperatures, a uPVC door will expand and contract which can cause problems locking the door and with the lock mechanism. Parts inside the lock mechanism and the lock gearbox can contract/expand making the lock feel stiffer then usual. If this is happening on a regular basis it would be wise to consider upgrading to a better quality door or door lock.
  • Adjust the door frame – doors can drop over time or debris can cause an obstructions in the frame stopping the door from closing snugly in the frame. Small stones and gravel from driveways are a common problem.
  • Check the frame and the locking points for any debris causing an obstruction. If the door has dropped you can adjust the hinges to realign the door and the locking points. Adjust the strike plate on the door if the door latch isn’t connecting into the frame.

How do I keep my door lock from sticking?

Don’t forget to maintain your lock on a regular basis to keep it from sticking.


  • Keep the door frame free of debris
  • Keep the door slab clean
  • Use a light machine oil on the hinges and lock

If you have problems with the door mechanism on your uPVC door, if the lock is stiff or difficult to turn at times, do not ignore it to avoid your lock failing and not being able to secure your front door.

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